Zinc deficiency in cereal crops is a significant issue for human health. Rice, being a staple food crop, could cause severe zinc deficiency. The use of zinc-solubilizing bacteria (ZSB) is an ecological tactic to raise bioavailable zinc in the soil that may alleviate yield loss and, subsequently, enhance the nutritional value of rice. In the presented study, treating rice plants with plant growth-promoting rhizobacteria S. marcescens FA-4 along with the recommended dose of chemical Zn and half dose of chemical Zn ensued under pot and field conditions at the COMSATS University, Islamabad, Pakistan. The obtained data indicated an augmentation in rice growth, yield, and grain zinc content in response to the S. marcescens FA-4 inoculation with and without the chemical Zn application. The S. marcescens FA-4 significantly enhanced the grain zinc content (21.4–27.7 mg kg^-1) under the pot and (18.7–30.1 mg kg^-1) under field conditions, with 1.5 to twofold rise in superoxide dismutase (SOD) and carbonic anhydrase (CA) activity in rice compared with the control. The rice plants treated with zinc solubilizing bacteria, followed by zinc treatments gave higher grain yields of 23.4–34.1 g pot^-1 and 3.2–3.6 t ha⁻¹ in rice cultivars, Basmati 385 and Super Basmati. The S. marcescens FA-4 with a half dose of chemical Zn also increased the zinc translocation index (1.4 to 1.7) toward grains. Consistency in the performance of zinc solubilizing bacteria occurred in the pot and field conditions. Hence, a conclusion that the use of zinc solubilizing strains is an efficient approach to enhance the zinc content of rice grains and combat the problem of zinc deficiency in humans.

Keywords: Zinc-solubilizing bacteria, superoxide dismutase, carbonic anhydrase, grain zinc content, rice

Key findings: The rice growth and yield increased in response to the combination of zinc solubilizing Serratia marcescens FA-4 and half a dose of chemical Zn. The Serratia marcescens FA-4 significantly enhanced the grain zinc content under the pot and field conditions, causing a 1.5 to twofold rise in superoxide dismutase (SOD) and carbonic anhydrase (CA) activity in rice compared with the control.